This invention relates to systems with media handling devices, such as printers, photocopiers, facsimile machines, scanners, and the like. More particularly, this invention relates to techniques for detecting overload conditions on collection trays utilized by the media handling devices.
Media handling devices facilitate media movement through a system. Typically, the media (e.g., paper, transparency, etc.) is transported from an input tray, through a media processing unit (e.g., scanning unit, printing mechanism, etc.), and output onto a collection tray. As collected, the media is commonly stacked sheet-by-sheet or job-by-job on the collection tray. In many conventional systems, the collection tray is manufactured using a low cost, durable material (e.g., plastic).
The media handling device may further include a tray adjustment mechanism that vertically moves the tray relative to the output slot. The tray is lowered as more sheets are deposited onto the stack and raised again after the operator removes an existing stack. The tray adjustment mechanism may be constructed using springs, motor, gears, belts, and/or other mechanical means to maneuver the tray relative to the output slot.
The tray and adjustment mechanism are designed to hold a specified maximum weight. A problem arises when the media stack collected on the tray exceeds this maximum weight, a condition known as xe2x80x9coverloadxe2x80x9d. For example, an operator may not notice the growing media stack on the collection tray and the combined weight of many sheets eventually exceeds the capacity of the collection tray, thereby triggering an overload condition. Another situation might be when the operator uses media of different weight and size. The system may not be able to discern the type and weight of the media and hence, may not be able to ascertain when the overload condition is approaching. When overload occurs, there is a possibility that the tray and/or adjustment mechanism may be damaged.
This invention addresses this overload problem in collection trays.
This invention concerns a system for detecting overload of a collection tray and recovering from the overload condition.
In one implementation, the system has a media handler that transports media (e.g., paper, transparencies, etc.) from an input bin through a processing unit to a collection tray. A tray adjustment mechanism moves the collection tray down and up as media is collected and occasionally removed by the operator. The tray adjustment mechanism is constructed, for example, using a mechanical coupling that attaches to the collection tray and a DC motor to drive the coupling and tray.
The system has a controller with an overload detector to detect when an overload condition arises and a recovery manager to recover from the overload condition. The overload detector indirectly measures the weight of the media collected on the collection tray by measuring the speed of the tray (or media stack) or alternatively, by monitoring the motor current. From this indirect weight measurement, the overload detector can ascertain whether the media stack on the tray is too heavy and will trigger an overload condition.
Once overload is detected, the controller stops the motor to avoid damage to the motor, coupling assembly, and/or tray. The controller then notifies the operator via a visual message and/or an audible alarm. The notification alerts the operator that the collection tray is overloaded and the media needs to be removed before operation can continue. The recovery manager is then invoked to periodically check whether the operator has removed the media and if so, return the tray to the appropriate position.
There are two different recovery situations: user-aided recovery and self-recovery. In user-aided recovery, the system awaits some explicit user input that the media stack has been removed, such as by requiring the operator to press a button or hold down a key. Self-recovery does not require explicit notice from the operator, but instead enables the system to check itself whether the media stack has been removed. With self-recovery, the recovery manager periodically attempts to move the collection tray. If the operator has not yet removed the stack, the tray will not move. But, if the operator has removed the media stack, the tray will be freed to move and can be recovered back to a proper operating position.